With the development of wireless multimedia services, high data rate and user experience are increasingly demanded by people, thereby making higher requirements on the system capacity and coverage of a traditional cellular network. In a traditional Long Term Evolution (LTE) cellular network, a macro eNB, serving as a unique access side network element, provides access service for a User Equipment (UE). In order to meet demands of a user for higher data rate and to improve the spectral efficiency of the cellular network, a 3rd Generation Partnership Project (3GPP) introduces a Low Power Node (LPN), serving as a supplement of the macro eNB, to provide access service for the UE. The LPN has the characteristics of low cost, low power, convenient deployment or the like, and usually has two deployment scenarios, namely a hot-spot deployment scenario and a coverage enhancement scenario, thereby effectively increasing the data rate of a high-rate data service in an indoor or outdoor hot-spot area, and improving the coverage of a remote area or a cell edge. Usually, the LPN may also be called as a small eNB, including a Home eNB (HeNB), a pico, a Remote Radio Unit/Remote Radio Head (RRU/RRH), a Relay Node (RN) or the like. Under the hot-spot deployment scenario, in order to achieve higher data rate and spectral efficiency, it is necessary to densely deploy a great number of small eNBs in an area. However, as the coverage range of a small cell under a small eNB is smaller, the probability of switching failure caused when a UE moving at an intermediate-high speed passes through the small eNB is increased, and the continuity of service for the UE is influenced. In order to improve the movement performance of the UE introduced into the small cell, it is proposed, in the industry, that a certain eNB such as the macro eNB ensures basic coverage. As shown in FIG. 1, the UE is always kept in Radio Resource Control (RRC) connection with the eNB, and the small cell only serves as a Transmission Point (TP) so as to provide a higher data rate and meet power saving demands from a user. Under this system architecture, the UE is at least kept in connection with two eNBs, and uses radio resources under the two eNBs, and cross-node radio resource aggregation may be achieved. This architecture is usually called as a dual-connection architecture. In the two eNBs connected with the UE, an eNB having a certain management control capacity is usually called as a Master eNB (MeNB), and the other eNB is called as a Secondary eNB (SeNB). When the UE has access to the MeNB, dual connection may be achieved by means of an SeNB addition flow. After the SeNB is added successfully, the SeNB may be subjected to a series of management such as SeNB modification, SeNB deletion and SeNB change.
A user plane has three possible architectures under the dual-connection architecture. As shown in FIG. 2, in an architecture option 1, an S1-U terminates at an MeNB and an SeNB; in an architecture option 2, the S1-U terminates at the MeNB, and no bearer separation exists at a Radio Access Network (RAN) side; and in an architecture option 3, the S1-U terminates at the MeNB, and bearer separation exists at the RAN side. For instance, after downlink data in an EPS bearer reaches the MeNB, some data in a bearer may be separated to the SeNB, and then is sent to the UE by the SeNB. According to a user plane protocol stack architecture of the SeNB, the above three architectures may be further subdivided. At present, dual connection may adopt an architecture 1A in the architecture option 1 or an architecture 3C in the architecture option 3. The architecture 1A is shown in FIG. 3. That is, the architecture option 1 is adopted, and a user plane protocol stack on the SeNB has an independent Packet Data Convergence Protocol (PDCP) layer and the following protocol layers including: a Radio Link Control (RLC) layer and a Media Access Control (MAC) layer, without bearer separation. The architecture 3C is shown in FIG. 4. That is, the architecture option 3 is adopted, and the user plane protocol stack on the SeNB has an independent RLC layer and the following protocol layer namely an MAC layer.
On the other hand, under the dual-connection architecture, an HeNB is probably used as the MeNB or the SeNB. Because the HeNB provides a service demand for only a specific user, a CSG concept is introduced, a unique identifier of each CSG being CSG ID. In LTE, the HeNB is defined with three cells having different access modes, namely a CSG cell (corresponding to a closed-mode HeNB, wherein only a UE registered as a CSG member can have access to it), a hybrid cell (corresponding to a hybrid-mode HeNB, wherein any terminal can have access to it, but a UE registered as a CSG member can have access to it with a higher-priority membership), and an open cell (corresponding to an open-mode HeNB, wherein any UE can have access to it). The access mode of the HeNB and the CSG ID may be obtained by broadcasting via an air interface. If the HeNB does not broadcast the CSG ID and a CSG indication, the cell refers to the open cell; if the HeNB broadcasts the CSG ID and a CSG indication of which the value is ‘true’, the cell refers to the CSG cell; and if the HeNB broadcasts the CSG ID and a CSG indication of which the value is ‘false’, the cell refers to the hybrid cell. A network element of a core network and a UE store CSG subscription information about a user, including a CSG ID list to which the user can have access as a membership. Under the dual-connection architecture, if the CSG subscription information about the user changes or expires, it is necessary to inform a corresponding MeNB or SeNB of an updated CSG identity state and to execute corresponding subsequent operations. For instance, if the identity of the UE in the closed cell is changed from a member to a non-member, the UE is no longer allowed to have access to the cell, and if the identity of the UE in the hybrid cell is changed from a member to a non-member, the Qos grade of the UE in the cell is reduced.